What if your cancer treatment could be made using the unique genetic fingerprint of your own tumour? That idea has moved a step closer to reality, after Merck and Moderna announced promising Phase 3 results for an experimental personalised cancer vaccine designed to help prevent melanoma from returning.

The treatment, called intismeran autogene, was formerly known as mRNA-4157 or V940. It is an individualised mRNA-based neoantigen therapy being developed in combination with Merck’s immunotherapy drug pembrolizumab, better known as Keytruda. In the latest Phase 3 INTerpath-001 trial, the combination showed statistically significant improvements in both recurrence-free survival (RFS) and distant metastasis-free survival (DMFS) compared with Keytruda alone in people with completely removed stage IIB to IV melanoma. But what makes this approach different from a conventional vaccine?

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That makes genomic testing an important part of the process. As Dr. Sharma points out, “detailed analysis of tumour genetics and immune biology is central to identifying the mutations that can guide such personalised treatment approaches.”

Melanoma is an aggressive form of skin cancer, and even after surgery successfully removes visible disease, there can be a risk that microscopic cancer cells remain and later cause the disease to return. That is where the combination of the personalised vaccine and Keytruda becomes particularly interesting.

According to Dr. Amit Bhargava, Director, Medical Oncology, Cancer Care, Medanta Mediclinic Defence Colony, the vaccine is designed to generate a tumour-specific immune response involving both CD8 and CD4 T cells. Keytruda, meanwhile, blocks the PD-1 immune checkpoint, helping prevent these cancer-fighting T cells from becoming suppressed. “The two work synergistically,” Dr. Bhargava says, explaining that Keytruda can help the activated T cells remain functional and target tumour cells more effectively.

The earlier Phase 2b KEYNOTE-942 study provided an important signal. At five years of follow-up, the combination was associated with a 49% reduction in the risk of recurrence or death and a 59% reduction in the risk of distant metastasis or death compared with Keytruda alone.

The new Phase 3 results strengthen that evidence, although the companies have not yet released the full detailed dataset. The trial will also continue to evaluate other outcomes, including overall survival.

That is one of the biggest questions surrounding the technology. Dr. Bhargava believes the development could be significant as genomic sequencing becomes increasingly sophisticated. “As genomic sequencing becomes more advanced and we are able to understand tumours at an even deeper molecular level, personalised approaches such as these could potentially deliver even better and more durable outcomes in the future,” he says. But there is still a considerable distance between promising clinical-trial results and routine treatment. Dr. Sharma cautions that “we still need to evaluate long-term survival data, regulatory review and results across other cancers before establishing its clinical use.”

In other words, this is not yet a universal ‘cancer vaccine’ available to patients. It is an investigational, highly personalised approach that combines tumour sequencing, mRNA technology and immunotherapy. Still, the idea marks a striking shift in cancer treatment: rather than asking which drug works best for a particular cancer type, researchers are increasingly asking what makes this individual patient’s tumour different, and can treatment be built around that difference?

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